The city of Montreal is planning to close two of its smaller freshwater treatment plants in Lachine and Dorval.

The city will spend the next ten years building 23 kilometres of water mains with a goal to eventually close the two smaller plants in favour of larger ones.

It's part of a plan that will cost the city about $235 million.

Officials say this will increase the production and the security of drinking water to Lachine and Dorval and lead to lower costs in the long term.

“It's much riskier – financially, not about the quality of the water, but financially – it's more risky to invest massively in those two plants than what we are going to do,” said Executive Committee member Sylvain Ouellet.

The plan means Dorval will eventually get its drinking water from Pointe-Claire while Lachine will be served from LaSalle and downtown.